bump piggieback version

[com.cemerick/piggieback "0.1.0"] isn't working for me (NullPointerExceptions in clojure.core/deref-future, see http://pastebin.com/GpfdCCaj), and I see that you're using piggieback 0.1.2 in your "resulting `project.clj` file." I'm guessing you actually want to use 0.1.2 everywhere.

Thanks again for all your work!

--matt
Merge pull request #111 from moquist/patch-5

bump piggieback version